<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<script>
			window.onload = function() {
				document.getElementById('userName').onblur = function() {
					alert("失去焦点！");
				}
			}
		</script>
	</head>
	<body>
		<input id="userName">
	</body>
</html>
